1. Field of the Invention
The present invention relates to a numerical control device that controls machine tools, and, more particularly, to a numerical control device that controls multiple paths at the same time by separating a plurality of manufacturing and work control processes such as lathing, milling, and loader control.
2. Description of the Related Art
Multi-path numerical control devices that simultaneously control a plurality of respective independent paths of manufacturing and work processes that include lathing, milling, and loader control are already commonly known. When an alarm is produced in one path, these multi-path numerical control devices either stop the operation of all the paths or continue the operation of all the paths other than the path in which the alarm was produced.
Further, in a single block operation, although the operation of a path to which a single block signal is inputted is stopped, the operation of other paths is continued. In view of this, it was proposed (See Japanese Patent Application Laid-Open No. H1-229305) that, if a single block signal is input while one block of a single-path manufacturing program is running, the manufacturing program is made to enter a single-block stoppage state while the manufacturing programs of other paths are controlled to a feed-hold state.
As mentioned above, with a conventional multi-path numerical control device, there are only two choices, which are to stop the operation of the path when an alarm is produced while continuing the operation of all the other paths, or to stop the operation of all the paths. Furthermore, with a single block stoppage operation, there are only two choices, too, which are to stop the operation of only the path with the single-block signal input and continue the operation of the other paths, or to stop the operation of the other paths in addition to the path with the single-block signal input, as disclosed in the above-mentioned Japanese Patent Application Laid Open No. H1-229305.
However, machines controlled by a multi-path numerical control device have paths associated with one another and unassociated paths that may be operated independently. In the case of associated paths, when an alarm is produced in one of these paths and the operation of this path is to be stopped, and when the operation of one path is to be stopped by means of single block stoppage, the operation of the other associated paths should be stopped. However, stoppage of unassociated paths is not required. Nevertheless, there is the problem that the work efficiency drops because, conventionally, the operation of all the paths including the operation of unassociated paths is stopped with stability in mind.